code: def test_step(self, batch, batch_idx):
      x, y = batch
      y_hat = self(x)
      loss = F.cross_entropy(y_hat, y)
      return loss
  
file_path: clearml/examples/frameworks/pytorch-lightning/pytorch_lightning_example.py
imports: import sys
  from argparse import ArgumentParser
  import pytorch_lightning
  import torch
  from torch.nn import functional
  from torch.utils.data import DataLoader, random_split
  from torchvision import transforms
  from torchvision.datasets.mnist import MNIST
  from clearml import Task
label_desc: Use image node_id 5 for calling the LitClassifier obj's underlying member method code with example usage: obj.test_step(batch, batch_idx) and returns: loss